Immune System

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Immune System

• Chapter 21

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Nonspecific Defenses

• Species resistance - docking sites on cells only
  allow certain pathogens to attach. Ex you cant
  get
• Tobacco mosaic virus
• Dutch elm disease
• Distemper

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• Mechanical Chemical Barriers
• 1st Line of Defense
• Skin and mucous membranes
• Stomach - HCl
• Tears - lysozyme
• Hair

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• 2nd Line of Defense
• Inflammation chemotactic proteins
• Phagocytosis macrophages and neutrophils

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• Natural Killer Cells tumor cells and cells with
  viral infections
• Interferon anti-viral proteins
• Complement Proteins causes lysis of antigen
• Fever

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2nd line of defense Inflammatory Process

• White blood cells (WBC) are released
• Monocytes, macrophages, neutrophils, eosinophils,
  natural killer cells
• Blood vessels expand near the wound or entry.
• Swelling occurs (caused by histamine) which
  increases body temperature to kill off pathogens
• Basophils released

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Specific Cellular Defenses

• Overview of Immune Response
• Humoral Immunity
• Provided by antibodies
• Produced by lymphocytes
• Bind to bacteria and free floating viruses

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• Cell Mediated Immunity
• Special lymphocytes direct the attack of infected
  cells
• Attack cancer cells, parasites, transplants
• Release chemicals to mediate OR stimulate other
  parts of the immune system

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• Antigens
• Large molecules that interact and respond to
  cells and immune chemicals
• Antibodies
• Native antigens immunoglobulins

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• Humoral Immunity (B-Cell Immunity)
• Produced in the bone marrow
• Produce antibodies
• Stimulated by antigens and/or lymphokines

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• 2 types of B cells
• Plasma cells make antibodies (2000/sec) and
  memory cells
• Memory cells remain for a lifetime to produce
  more antibodies if antigen returns

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• Antibodies
• 5 classes
• IgD attached to B cells act as a receptor
  sites
• IgM RBC, food and bacterial markers stimulates
  complement proteins agglutinating agent

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• IgG main antibody tissue marker, virus,
  bacteria and toxin antibody
• IgA found in milk, tears, urine, sweat
  prevents attachment of pathogens to epithelial
  tissues
• IgE associated with allergies cause release of
  histamine

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• Responsible for 1o and 2o immune response
• 1o - initial exposure to antigen, plasma cells
  produce antibodies lag time
• 2o subsequent exposure to previous antigen
  produce 1000s of antibodies within hours

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• Types of Antibody Immunity
• Acquired Immunity
• Active artificial vaccine of the antigen
  (measles) requires boosters
• Passive artificial vaccine of antibodies from
  another infected animal (rabies)

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• Natural Immunity
• Active natural get the disease lifetime
  immunity
• Passive natural mothers antibodies are passed
  to fetus prior to birth short-term

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• Cell-Mediated Immunity
• T cells
• Originate and mature in the thymus
• Must become tolerant to bodys own proteins so
  as not to react to them
• Can only recognize an antigen when it is bound
  to another immune cell

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• Secrete lymphokines to stimulate cloning of
  other immune cells
• 4 types
• Cytotoxic (killer) T cells secrete perforin
  which lyses target cells
• Helper T cells direct cloning of other T B
  cells through secretion of lymphokines

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• Suppressor T cells dampens activity of killer
  helper cells
• Delayed hypersensitivity T cells play role in
  allergies and chronic inflammation

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Organ Transplants

• 4 Types of transplants (grafts)
• Autografts self to self always successful
• Isografts identical twins always successful

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• Allografts same species used most often
  complications due to tissue typing
• Xenografts different species rarely successful

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• Following transplantation
• Anti-inflammatory drugs
• Cytotoxic drugs
• Radiation
• Cyclosporin to suppress production of
  interleukins, Helper T and Cytotoxic T cells
  without stopping production of already sensitized
  B cells

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• Rejection
• Early inadequate blood supply to graft
• Late burst of unexplained antibodies

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Homeostatic Imbalances

• Immunodeficiencies
• Autoimmunity

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• Hypersensitivities body responds to a harmless
  antigen
• Immediate hypersensitivity- within minutes
• Cytotoxic hypersensitivity transfusion reactions

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• Immune-complex hypersensitivity strep, malaria,
  chronic viral infections cause rashes, swollen
  lymph nodes
• Delayed hypersensitivity poison ivy, cosmetics